Sesamol attenuates genotoxicity in bone marrow cells of whole-body γ-irradiated mice

Genotoxicity of Formaldehyde: Effect of Whole-Body Exposure on Polychromatic Erythrocyte/Normochromatic Erythrocyte Ratio in Male and Female Rats

Every day, millions of individuals are exposed to formaldehyde (FA) due to its extensive presence and versatile use. Many in vivoand in vitroexperiments revealed that the mechanism of genotoxicity induced by FA exposure is complex yet toxicity upon whole-body exposure (WBE) to FA is less. As teachers, students, and skilled assistants in the health care sectors are also extensively exposed to FA vapors, it might result in genotoxicity. However, the effects of subchronic exposure to FA at low concentrations are not clear. Hence, analysis of the micronucleus (MN) was necessary to study the genetic toxicity triggered by FA in the bone marrow of male and female experimental rats. The present study is a gender- and duration of exposure-based assessment of the geno- and cytotoxicity in bone marrow cells of Wistar rats to study the effect of WBE to 10% FA on polychromatic erythrocytes/normochromatic erythrocytes (PCE/NCE) ratio and micronucleated polychromatic erythrocytes (MnPCE) in experimental rats. The obtained result clearly showed that WBE to FA for 60 days at concentrations between 1 and 1.1 ppm (0, 1, and 1.5 h) induced genotoxic effects in both male and female rats by altering the MnPCE% and significantly increasing the ratio of PCE/NCE (1.07 ± 0.23, 1.20 ± 0.20, 1.22 ± 0.14). The PCE/NCE ratio in male rats was lesser (0.98, 1.12, and 1.18) when compared with female rats (1.17, 1.29, and 1.26) with 0, 1, and 1.5 h exposure, respectively. Thus, the genetic/cellular sensitivity to FA differs among the sexes and also depends on the exposure duration.

Repeated dose toxicity studies of Trichostatin A in Swiss albino mice through oral and intravenous route of administration with special emphasis on genotoxicity

Intravenous and oral 14 d repeated dose toxicity studies of Trichostatin A (TSA) were carried out in Swiss albino mice using low, intermediate, and high doses. Intravenous doses were 10, 25, and 50 μg/kg b.w while the oral doses were 20, 50, and 100 μg/kg b.w. Respective control groups of mice were administered phosphate buffered saline (vehicle only) for 14 consecutive days. All external morphological, hematological, biochemical, urine, histopathological, food intake in addition to body weight and vital organ weight were recorded. During the study no mortality in any animal was observed in either treatment routes. There were no significant changes in morphology, food intake, hematology, biochemical, urine analysis, organ weight. Animals treated high dose of TSA intravenously (50 μg/kg b.w) and orally (100 μg/kg b.w) had enlarged, congested, and discolored kidneys which were statistically significant. Histopathological studies had shown statistically significant degenerated glomerulus in high dose of intravenous and orally treated animals and degenerated tubule were found in orally treated animals. Genotoxicity was evaluated using micronucleus frequency at 14 and 21 d after treatment and chromosomal aberration at 21 d after treatment. Micronucleaus assay and chromosomal assay however did not show any significant changes at any doses and administration routes. Therefore, this study concludes that dose ∼25 µg/kg and ∼50 µg/kg b.w may be considered as No Observed Adverse Effect Level (NOAEL) for intravenous and oral administration of TSA respectively.

Sesamol as a potential candidate for the treatment of hepatic fibrosis, based on its regulation of FXR/LXR axis-mediated inhibition of autophagy through crosstalk between hepatic cells and macrophage

BACKGROUND

Sesamol (SEM), a natural lignan compound isolated from sesame, has strong anti-oxidant property, regulating lipid metabolism, decreasing cholesterol and hepatoprotection. However, its anti-hepatic fibrosis effect and mechanisms have not been comprehensively elucidated.

HYPOTHESIS/PURPOSE

This study aims to investigate the anti-hepatic fibrosis of SEM and its underlying mechanisms.

METHOD

C57BL/6 mice with hepatic fibrosis were induced by TAA, then administrated with SEM or curcumin, respectively. HSCs were stimulated by TGF-β or conditioned medium, and then cultured with SEM, GW4064, GW3965, Rapamycin (RA) or 3-methyladenine (3-MA), respectively. Mice with hepatic fibrosis also were administrated with SEM, RA or 3-MA to estimate the effect of SEM on autophagy.

RESULTS

In vitro, SEM significantly inhibited extracellular matrix deposition, P2 × 7r-NLRP3, and inflammatory cytokines. SEM increased FXR and LXRα/β expressions and decreased MAPLC3α/β and P62 expressions, functioning as 3-MA (autophagy inhibitor). In vivo, SEM reduced serum transaminase, histopathology changes, fibrogenesis, autophagy markers and inflammatory cytokines caused by TAA. LX-2 were activated with conditioned medium from LPS-primed THP-1, which resulted in significant enhance of autophagy markers and inflammatory cytokines and decrease of FXR and LXRα/β expressions. SEM could reverse above these changes and function as 3-MA, GW4064, or GW3965. Deficiency of FXR or LXR attenuated the regulation of SEM on α-SMA, MAPLC3α/β, P62 and IL-1β in activated LX-2. In activated THP-1, deficiency of FXR could decrease the expression of LXR, and vice versa. Deficiency of FXR or LXR in activated MΦ decreased the expressions of FXR and LXR in activated LX-2. Deficiency FXR or LXR in activated MΦ also attenuated the regulation of SEM on α-SMA, MAPLC3α/β, P62, caspase-1 and IL-1β. In vivo, SEM significantly reversed hepatic fibrosis via FXR/LXR and autophagy.

CONCLUSION

SEM could regulate hepatic fibrosis by inhibiting fibrogenesis, autophagy and inflammation. FXR/LXR axis-mediated inhibition of autophagy contributed to the regulation of SEM against hepatic fibrosis, especially based on involving in the crosstalk of HSCs-macrophage. SEM might be a prospective therapeutic candidate, and its mechanism would be a new direction or strategy for hepatic fibrosis treatment.

Nrf2-regulated antioxidant response ameliorating ionizing radiation-induced damages explored through in vitro and molecular dynamics simulations

This study aims to investigate the mechanism of natural antioxidant ferulic acid (FA) in reducing oxidative stress followed by its inhibitory effect on the Keap1-Nrf2 complex. FA was treated ex vivo with human blood for 30 min at 37 °C ± 1 °C and exposed to 1.5 Gy of γ- rays of 60Co (0.789 Gy/min) and allowed for repair for an hour at 37 °C ± 1 °C. FA's free radical scavenging capacity was measured using 2,7-dichlorofluorescein diacetate assay and cytogenetic assays. Further, a possible mechanism of protein-ligand interaction between FA and Keap1-Nrf2 pathway protein as a cellular drug target was studied using docking and molecular dynamics simulation. The 1.5 Gy of γ- rays exposed to pre-treated blood with FA showed a significant (p < 0.05) reduction in reactive oxygen species and DNA damage compared to the normal control blood group sample. The ligand-protein transient binding interaction in molecular dynamic simulation over a period of 100 ns was consistent and stable emphasizing complementary charge between the protein and ligand, speculating higher hydrophobic amino acid residues in the Keap1 active pocket. This might sway the Keap1 from interaction with Nrf2, and could lead to nuclear translocation of Nrf2 during radiation-induced oxidative stress. The present study emphasizes the radioprotective effect of FA against 1.5 Gy of γ- rays exposed to human blood and the application of in silico approaches helpful for the possible protective effect of FA.Communicated by Ramaswamy H. Sarma.

Marasmius androsaceus mitigates depression-exacerbated intestinal radiation injuries through reprogramming hippocampal miRNA expression

INTRODUCTION

Cancer patients commonly experience high levels of psychological stress, which poses significant risks to their well-being. Radiotherapy is a primary treatment modality for cancer; however, it often leads to intestinal injuries in these patients. Nevertheless, the impact of mental stress on radiotherapy-intertwined complications remains unclear.

METHODS

To induce intestinal injury, we employed total abdominal irradiation in our experimental model. We conducted high-throughput sequencing to analyze the expression profile of miRNAs in the hippocampus.

RESULTS

We observed that mice with depression exhibited more severe intestinal injuries following total abdominal irradiation. Remarkably, oral administration of Marasmius androsaceus not only alleviated the depressive phenotype but also mitigated radiation-induced intestinal toxicity. Notably, this radioprotective effect was not observed in mice without depression. Depression disrupted the hippocampal miRNA expression profile in mice subjected to local irradiation of the abdomen, leading to the accumulation of miR-139-5p and miR-184-3p in the hippocampus, serum, and small intestine tissues. However, treatment with Marasmius androsaceus reprogrammed the miRNA expression signature in mice with depression. Furthermore, intravenous injection of antagomirs targeting miR-139-5p and miR-184-3p ameliorated depression, up-regulated Spn expression, reduced radiation enteritis, and improved the integrity of the small intestine in irradiated mice.

CONCLUSION

Our findings demonstrate the efficacy of Marasmius androsaceus, a small mushroom, in alleviating depression-aggravated intestinal toxicity following radiotherapy by reprogramming hippocampal miRNA expression.

Exploring Natural Products as Radioprotective Agents for Cancer Therapy: Mechanisms, Challenges, and Opportunities

Radiotherapy is an important cancer treatment. However, in addition to killing tumor cells, radiotherapy causes damage to the surrounding cells and is toxic to normal tissues. Therefore, an effective radioprotective agent that prevents the deleterious effects of ionizing radiation is required. Numerous synthetic substances have been shown to have clear radioprotective effects. However, most of these have not been translated for use in clinical applications due to their high toxicity and side effects. Many medicinal plants have been shown to exhibit various biological activities, including antioxidant, anti-inflammatory, and anticancer activities. In recent years, new agents obtained from natural products have been investigated by radioprotection researchers, due to their abundance of sources, high efficiency, and low toxicity. In this review, we summarize the mechanisms underlying the radioprotective effects of natural products, including ROS scavenging, promotion of DNA damage repair, anti-inflammatory effects, and the inhibition of cell death signaling pathways. In addition, we systematically review natural products with radioprotective properties, including polyphenols, polysaccharides, alkaloids, and saponins. Specifically, we discuss the polyphenols apigenin, genistein, epigallocatechin gallate, quercetin, resveratrol, and curcumin; the polysaccharides astragalus, schisandra, and Hohenbuehelia serotina; the saponins ginsenosides and acanthopanax senticosus; and the alkaloids matrine, ligustrazine, and β-carboline. However, further optimization through structural modification, improved extraction and purification methods, and clinical trials are needed before clinical translation. With a deeper understanding of the radioprotective mechanisms involved and the development of high-throughput screening methods, natural products could become promising novel radioprotective agents.

Quantitative assessment of antioxidant potential of selected homeopathic preparations in clinical practice

OBJECTIVES

Antioxidant property like radical scavenging is a primary target to elucidate the efficacy mechanism of a drug against diseases linked to oxidative stress such as cancer, metabolic disorders, rheumatoid arthritis, etc. In alternative therapies, homeopathy is one of the preferred choices by patients and clinicians due to its potential to cure chronic and complex illnesses. However, the efficacy of homeopathic preparations at high diluted potencies attracts rational criticism due to insufficient scientific knowledge supporting the mechanism of action. Therefore, an attempt was made to estimate the total phenolic content (TPC) and radical scavenging activity of clinically prescribed homeopathic drugs.

METHODS

With gallic acid as a reference control, mother tinctures (MTs) and different potencies of Eucalyptus globulus (EG), Syzygium jambolanum (SJ), Ruta graveolens (RG), and Thuja occidentalis (TO) were used to perform Folin-Ciocalteu test, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays.

RESULTS

The results showed TPC of MTs equivalent to µg/mL of gallic acid viz; EG (4,872.5 ± 133.2), SJ (8,840.5 ± 14.8), RG (985.6 ± 39.1), and TO (341.5 ± 19.5) with significant ABTS and DPPH radical scavenging potential. Whereas 30C and 200C potencies of each homeopathic drug showed undetectable phenolic content and insignificant radical scavenging potential compared to vehicle control, i.e., alcohol 90% (2.0 ± 1.5).

CONCLUSIONS

The reported efficacy of 30C and 200C potencies of homeopathic medicines against oxidative stress-related illnesses might be due to mechanisms other than radical scavenging. Furthermore, the assays studied can be helpful in drug standardization and quality control of MTs that are used as starting material in homeopathic preparations.

High-throughput screening strategies for space-based radiation countermeasure discovery

As humanity begins to venture further into space, approaches to better protect astronauts from the hazards found in space need to be developed. One particular hazard of concern is the complex radiation that is ever present in deep space. Currently, it is unlikely enough spacecraft shielding could be launched that would provide adequate protection to astronauts during long-duration missions such as a journey to Mars and back. In an effort to identify other means of protection, prophylactic radioprotective drugs have been proposed as a potential means to reduce the biological damage caused by this radiation. Unfortunately, few radioprotectors have been approved by the FDA for usage and for those that have been developed, they protect normal cells/tissues from acute, high levels of radiation exposure such as that from oncology radiation treatments. To date, essentially no radioprotectors have been developed that specifically counteract the effects of chronic low-dose rate space radiation. This review highlights how high-throughput screening (HTS) methodologies could be implemented to identify such a radioprotective agent. Several potential target, pathway, and phenotypic assays are discussed along with potential challenges towards screening for radioprotectors. Utilizing HTS strategies such as the ones proposed here have the potential to identify new chemical scaffolds that can be developed into efficacious radioprotectors that are specifically designed to protect astronauts during deep space journeys. The overarching goal of this review is to elicit broader interest in applying drug discovery techniques, specifically HTS towards the identification of radiation countermeasures designed to be efficacious towards the biological insults likely to be encountered by astronauts on long duration voyages.

Phytochemicals: A potential next generation agent for radioprotection

BACKGROUND

Radiation hazards are accountable for extensive damage in the biological system and acts as a public health burden. Owing to the rapid increasing in radiation technology, both Ionizing radiation (IR) from natural and man made source poses detrimental outcome to public health. IR releases free radicals which induces oxidative stress and deleterious biological damage by modulating radiation induced signalling intermediates. The efficacy of existing therapeutic approach and treatment strategy are limited owing to their toxicity and associated side effects. Indian system of traditional medicine is enriched with prospective phytochemicals with potential radioprotection ability.

PURPOSE

The present review elucidated and summarized the potential role of plant derived novel chemical compound with prospective radioprotective potential.

METHOD

So far as the traditional system of Indian medicine is concerned, plant kingdom is enriched with potential bioactive molecules with diverse pharmacological activities. We reviewed several compounds mostly secondary metabolites from plant origin using various search engines.

RESULTS

Both compounds from land plants and marine source exhibited antioxidant antiinflammatory, free radical scavenging ability. These compounds have tremendous potential in fine-tuning of several signalling intermediates, which are actively participated in the progression and development of a pathological condition associated with radiation stress.

CONCLUSION

Development and explore of an operational radioprotective agent from originated from plant source that can be used as a novel molecular tool to eliminate the widespread damage caused by space exploration, ionizing radiation, nuclear war and radiotherapy has been significantly appreciated. Through extensive literature search we highlighted several compounds from both land plant and marine origin can be implemented for a better therapeutic potential against radiation induced injury. Furthermore, extensive clinical trials must be carried out in near future for better therapeutic modality and clinical efficacy.

Protection of the hematopoietic system against radiation-induced damage: drugs, mechanisms, and developments

Sometimes, people can be exposed to moderate or high doses of radiation accidentally or through the environment. Radiation can cause great harm to several systems within organisms, especially the hematopoietic system. Several types of drugs protect the hematopoietic system against radiation damage in different ways. They can be classified as "synthetic drugs" and "natural compounds." Their cellular mechanisms to protect organisms from radiation damage include free radical-scavenging, anti-oxidation, reducing genotoxicity and apoptosis, and alleviating suppression of the bone marrow. These topics have been reviewed to provide new ideas for the development and research of drugs alleviating radiation-induced damage to the hematopoietic system.

Radiomitigation by Melatonin in C57BL/6 Mice: Possible Implications as Adjuvant in Radiotherapy and Chemotherapy

BACKGROUND/AIM

Melatonin (N-acetyl-5-methoxytryptamine), a chief secretory molecule of the pineal gland, has multiple properties, and numerous clinical investigations regarding its actions are in progress. This study investigated the radiomitigative role of melatonin in C57BL/6 mice.

MATERIALS AND METHODS

Melatonin (100 mg/kg) was orally administered once daily starting at 1 h on day 1 and subsequently every 24 h until day 7 after whole-body irradiation (WBI) and survival was monitored for 30 days. The bone marrow, spleen, and intestine were studied to evaluate the mitigative potential of melatonin after radiation-induced damage.

RESULTS

Melatonin significantly improved the survival upto 60% and 90% after 9 Gy (lethal) and 7.5 Gy (sub-lethal) WBI, respectively. Melatonin alleviated WBI-induced myelosuppression and pancytopenia, and increased white blood cell, red blood cell, platelet, and lymphocyte (CD4⁺ and CD8⁺) counts in peripheral blood. Bone marrow and spleen cellularity were restored through enhanced haematopoiesis. Melatonin ameliorated the damage in the small intestine, and promoted recovery of villi length, crypts number, and goblet cell count.

CONCLUSION

Melatonin mitigates the radiation-induced injury in the gastrointestinal and haematopoietic systems. The observed radiomitigative properties of melatonin can also be useful in the context of adjuvant therapy for cancer and radiotherapy.

Role of melatonin mediated G-CSF induction in hematopoietic system of gamma-irradiated mice

AIMS

Hematopoietic acute radiation syndrome (H-ARS) can cause lethality, and therefore, the necessity of a safe radioprotector. The present study was focused on investigating the role of melatonin in granulocytes colony-stimulating factor (G-CSF) and related mechanisms underlying the reduction of DNA damage in hematopoietic system of irradiated mice.

MAIN METHODS

C57BL/6 male mice were exposed to 2, 5, and 7.5Gy of whole-body irradiation (WBI), 30 min after intra-peritoneal administration of melatonin with different doses. Mice were sacrificed at different time intervals after WBI, and bone marrow, splenocytes, and peripheral blood lymphocytes were isolated for studying various parameters including micronuclei (MN), cell cycle, comet, γ-H2AX, gene expression, amino acid profiling, and hematology.

KEY FINDINGS

Melatonin100mg/kg ameliorated radiation (7.5Gy and 5Gy) induced MN frequency and cell death in bone marrow without mortality. At 24 h of post-WBI (2Gy), the frequency of micronucleated polychromatic erythrocytes (mnPCE) with different melatonin doses revealed 20 mg/kg as optimal i.p. dose for protecting the hematopoietic system against radiation injury. In comet assay, a significant reduction in radiation-induced % DNA tail (p ≤ 0.05) was observed at this dose. Melatonin reduced γ-H2AX foci/cell and eventually reached to the control level. Melatonin also decreased blood arginine levels in mice after 24 h of WBI. The gene expression of G-CSF, Bcl-2-associated X protein (BAX), and Bcl2 indicated the role of melatonin in G-CSF regulation and downstream pro-survival pathways along with anti-apoptotic activity.

SIGNIFICANCE

The results revealed that melatonin recovers the hematopoietic system of irradiated mice by inducing G-CSF mediated radioprotection.

Natural radioprotectors on current and future perspectives: A mini-review

Radiation therapy is used as the primary treatment for cancer. Eighty percent of cancer patients require radiation therapy during treatment or for medical purposes. During treatment, radiation causes various biological defects in the cells. The prevalence of cytotoxicity limits the dose used for effective treatment. This method is designed to strike a balance between removing cancer cells and protecting normal tissues. Unfortunately, effective radiation is unavailable once acute toxicity occurs during clinical radiation therapy. Therefore, a lot of research interest is needed in the discovery of radioprotective drugs to accelerate treatment to reduce this toxicity (i.e., normal tissue toxicity to cancer cell death). Radiation protectors may be chemicals or drugs that minimize the damage caused due to radiation therapy in living organisms. The determination of effective and nontoxic radiation protection is an essential goal for radiation oncologists and basic radiobiologists. However, despite the advantages, many radioprotectors were found to have disadvantages which include cost, less duration, toxicity, and effect on the central nervous system. Therefore in recent years, the focus has been diverted to finding out optimal natural products to act as radioprotectors. Natural radiation protectors are plant compounds that protect normal (noncancerous) cells from damage from radiation therapy. Natural herbal products are nontoxic with proven therapeutic benefits and have long been used to treat various diseases. In conclusion, we find that there are various radiation protectors with different purposes and mechanisms of action.

Repurposing sodium diclofenac as a radiation countermeasure agent: A cytogenetic study in human peripheral blood lymphocytes

We assessed the radioprotective and mitigative actions of sodium diclofenac, a non-steroidal anti-inflammatory drug using cultured human peripheral blood as a model. Both pre- and post-irradiation treatments with the drug reduced gamma radiation-induced formation of dicentric chromosome, cytochalasin-blocked micronuclei and γ-H2AX foci in human peripheral blood lymphocytes. This work supports the concept that sodium diclofenac may be a useful radiation countermeasure agent.

Protection from ionizing radiation-induced genotoxicity and apoptosis in rat bone marrow cells by HESA-A: a new herbal-marine compound

HESA-A is an herbal-marine compound which improves the quality of life of end-stage cancer patients. The aim of the present study was to evaluate the possible protective effect of HESA-A against IR-induced genotoxicity and apoptosis in rat bone marrow. Rats were given HESA-A orally at doses of 150 and 300 mg/kg body weight for seven consecutive days. On the seventh day, the rats were irradiated with 4 Gy X-rays at 1 h after the last oral administration. The micronucleus assay, reactive oxygen species (ROS) level analysis, hematological analysis and flow cytometry were used to assess radiation antagonistic potential of HESA-A. Administration of 150 and 300 mg/kg of HESA-A to irradiated rats significantly reduced the frequencies of micronucleated polychromatic erythrocytes (MnPCEs) and micronucleated normochromatic erythrocytes (MnNCEs), and also increased PCE/(PCE + NCE) ratio in bone marrow cells. Moreover, pretreatment of irradiated rats with HESA-A (150 and 300 mg/kg) significantly decreased ROS level and apoptosis in bone marrow cells, and also increased white blood cells count in peripheral blood. For the first time in this study, it was observed that HESA-A can have protective effects against radiation-induced genotoxicity and apoptosis in bone marrow cells. Therefore, HESA-A can be considered as a candidate for future studies to reduce the side effects induced by radiotherapy in cancer patients.

Sesamol, a major lignan in sesame seeds (Sesamum indicum): Anti-cancer properties and mechanisms of action

Sesamol is a natural phenolic compound and a major lignan isolated from sesame seeds (Sesamum indicum) and sesame oil. The therapeutic potential of sesamol was investigated intensively, and there is compelling evidence that sesamol acts as a metabolic regulator that possesses antioxidant, anti-mutagenic, anti-hepatotoxic, anti-inflammatory, anti-aging, and chemopreventive properties. Various studies have reported that sesamol exerts potent anti-cancer effects. Herein, we provide a comprehensive review that summarizes the in vitro and in vivo anti-cancer activity of sesamol in several cancer cell lines and animal models. The protective role that sesamol plays against oxidative stress through its radical scavenging ability and lipid peroxidation lowering potential is analyzed. The ability of sesamol to regulate apoptosis and various stages of the cell cycle is also outlined. Moreover, the signaling pathways that sesamol seems to target to execute its antioxidant, anti-inflammatory, and pro-apoptotic/anti-proliferative roles are discussed. The signaling pathways that sesamol targets include the p53, MAPK, JNK, PI3K/AKT, TNFα, NF-κB, PPARγ, caspase-3, Nrf2, eNOS, and LOX pathways. The mechanisms of action that sesamol executes to deliver its anti-cancer effects are delineated. In sum, there is ample evidence suggesting that sesamol possesses potent anti-cancer properties in vitro and in vivo. A thorough understanding of the molecular targets of sesamol and the mechanisms of action underlying its anti-cancer effects is necessary for possible employment of sesamol as a chemotherapeutic agent in cancer prevention and therapy.

The comet assay in animal models: From bugs to whales - (Part 2 Vertebrates)

The comet assay has become one of the methods of choice for the evaluation and measurement of DNA damage. It is sensitive, quick to perform and relatively affordable for the evaluation of DNA damage and repair at the level of individual cells. The comet assay can be applied to virtually any cell type derived from different organs and tissues. Even though the comet assay is predominantly used on human cells, the application of the assay for the evaluation of DNA damage in yeast, plant and animal cells is also quite high, especially in terms of biomonitoring. The present extensive overview on the usage of the comet assay in animal models will cover both terrestrial and water environments. The first part of the review was focused on studies describing the comet assay applied in invertebrates. The second part of the review, (Part 2) will discuss the application of the comet assay in vertebrates covering cyclostomata, fishes, amphibians, reptiles, birds and mammals, in addition to chordates that are regarded as a transitional form towards vertebrates. Besides numerous vertebrate species, the assay is also performed on a range of cells, which includes blood, liver, kidney, brain, gill, bone marrow and sperm cells. These cells are readily used for the evaluation of a wide spectrum of genotoxic agents both in vitro and in vivo. Moreover, the use of vertebrate models and their role in environmental biomonitoring will also be discussed as well as the comparison of the use of the comet assay in vertebrate and human models in line with ethical principles. Although the comet assay in vertebrates is most commonly used in laboratory animals such as mice, rats and lately zebrafish, this paper will only briefly review its use regarding laboratory animal models and rather give special emphasis to the increasing usage of the assay in domestic and wildlife animals as well as in various ecotoxicological studies.

PK-PD based optimal dose and time for orally administered supra-pharmacological dose of melatonin to prevent radiation induced mortality in mice

AIMS

The study reports preclinical pharmacokinetics (PK) and correlation with pharmacological effect at suprapharmacological dose of orally administered melatonin along with time and dose optimization, which have been lacking in earlier reports of radioprotection using melatonin.

METHODS

PK of melatonin in C57BL/6 mice was evaluated after dose of 250 mg/kg using HPLC. Tissue distribution study was conducted in vital organs following oral administration. Plasma total antioxidant capacity (TAC) was determined by ABTS⁺ radical assay and was correlated to plasma concentrations of melatonin. Using the outcomes of PK and Pharmacodynamics (PD), survival study was conducted for optimization of 'drug radiation gap period' (DRGP). Optimal oral dose for radioprotection was determined using survival as an end point.

KEY FINDINGS

PK analysis of melatonin revealed T_max at 5 min with closely spaced another distinct concentration peak at 20 min. Plasma TAC of melatonin showed similar peaks at 5 min and 45 min, with the highest TAC at 45 min. Survival following a lethal (9 Gy) radiation dose was 20% and 40% after 5 and 45 min of melatonin administration, respectively. DRGP for melatonin was thus 45 min, while optimal oral dose ranged from 125 to 250 mg/kg. PK parameters at 250 mg/kg dose were qualitatively similar to low dose of melatonin, thus preventing chances of unexpected toxicity.

SIGNIFICANCE

Survival enhancement at 45 min suggested as probable interval required as 'DRGP'. The optimum oral therapeutic window appears large with no substantial toxicity. The outcomes will be useful in development of radioprotectors as well as other therapeutic applications.

Pharmacology of natural radioprotectors

Radiotherapy is one of the most efficient ways to treat cancer. However, deleterious effects, such as acute and chronic toxicities that reduce the quality of life, may result. Naturally occurring compounds have been shown to be non-toxic over wide dose ranges and are inexpensive and effective. Additionally, pharmacological strategies have been developed that use radioprotectors to inhibit radiation-induced toxicities. Currently available radioprotectors have several limitations, including toxicity. In this review, we present the mechanisms of proven radioprotectors, ranging from free radical scavenging (the best-known mechanism of radioprotection) to molecular-based radioprotection (e.g., upregulating expression of heat shock proteins). Finally, we discuss naturally occurring compounds with radioprotective properties in the context of these mechanisms.

Sesamol ameliorates radiation induced DNA damage in hematopoietic system of whole body γ-irradiated mice

Ionizing radiation exposure is harmful and at high doses can lead to acute hematopoietic radiation syndrome. Therefore, agents that can protect hematopoietic system are important for development of radioprotector. Sesamol is a potential molecule for development of radioprotector due to its strong free radical scavenging and antioxidant properties. In the present study, sesamol was evaluated for its role in DNA damage and repair in hematopoietic system of γ-irradiated CB57BL/6 mice and compared with amifostine. C57BL/6 male mice were administered with sesamol 20 mg/kg (i.p.) followed by 2 Gy whole body irradiation (WBI) at 30 min. Mice were sacrificed at 0.5, 3, 24 h postirradiation; bone marrow, splenocytes, and peripheral blood lymphocytes were isolated to measure DNA damages and repair using alkaline comet,γ-H2AXand micronucleus assays. An increase in % of tail DNA was observed in all organs of WBI mice. Whereas in pre-administered sesamol reduced %DNA in tail (P ≤ 0.05). Sesamol has also reduced formation of radiation induced γ-H2AX foci after 0.5 h in these organs and further lowered to respective control values at 24 h of WBI. Similar reduction of % DNA in tail and γ-H2AX foci were observed with amifostine (P ≤ 0.05). Analysis of mnPCE frequency at 24 h has revealed similar extent of protection by sesamol and amifostine. Interestingly, both sesamol and amifostine, alone and with radiation, also increased the granulocytes count significantly compared to the control (P ≤ 0.05). These findings suggest that sesamol has strong potential to protect hematopoietic system by lowering radiation induced DNA damages and can prevent acute hematopoietic syndrome in mice. Environ. Mol. Mutagen. 59:79-90, 2018. © 2017 Wiley Periodicals, Inc.

Appraisal of biochemical classes of radioprotectors: evidence, current status and guidelines for future development

The search for efficient radioprotective agents to protect from radiation-induced toxicity, due to planned or accidental radiation exposure, is still ongoing worldwide. Despite decades of research and development of widely different biochemical classes of natural and derivative compounds, a safe and effective radioprotector is largely unmet. In this comprehensive review, we evaluated the evidence for the radioprotective performance of classical thiols, vitamins, minerals, dietary antioxidants, phytochemicals, botanical and bacterial preparations, DNA-binding agents, cytokines, and chelators including adaptogens. Where radioprotection was demonstrated, the compounds have shown moderate dose modifying factors ranging from 1.1 to 2.7. To date, only few compounds found way to clinic with limited margin of dose prescription due to side effects. Most of these compounds (amifostine, filgratism, pegfilgrastim, sargramostim, palifermin, recombinant salmonella flagellin, Prussian blue, potassium iodide) act primarily via scavenging of free radicals, modulation of oxidative stress, signal transduction, cell proliferation or enhance radionuclide elimination. However, the gain in radioprotection remains hampered with low margin of tolerance. Future development of more effective radioprotectors requires an appropriate nontoxic compound, a model system and biomarkers of radiation exposure. These are important to test the effectiveness of radioprotection on physiological tissues during radiotherapy and field application in cases of nuclear eventualities.

Protective Effects of Hydrogen against Low-Dose Long-Term Radiation-Induced Damage to the Behavioral Performances, Hematopoietic System, Genital System, and Splenic Lymphocytes in Mice

Molecular hydrogen (H₂) has been previously reported playing an important role in ameliorating damage caused by acute radiation. In this study, we investigated the effects of H₂ on the alterations induced by low-dose long-term radiation (LDLTR). All the mice in hydrogen-treated or radiation-only groups received 0.1 Gy, 0.5 Gy, 1.0 Gy, and 2.0 Gy whole-body gamma radiation, respectively. After the last time of radiation exposure, all the mice were employed for the determination of the body mass (BM) observation, forced swim test (FST), the open field test (OFT), the chromosome aberration (CA), the peripheral blood cells parameters analysis, the sperm abnormality (SA), the lymphocyte transformation test (LTT), and the histopathological studies. And significant differences between the treatment group and the radiation-only groups were observed, showing that H₂ could diminish the detriment induced by LDLTR and suggesting the protective efficacy of H₂ in multiple systems in mice against LDLTR.

Pine polyphenols from Pinus koraiensis prevent injuries induced by gamma radiation in mice

Pine polyphenols (PPs) are bioactive dietary constituents that enhance health and help prevent diseases through antioxidants. Antioxidants reduce the level of oxidative damages caused by ionizing radiation (IR). The main purpose of this paper is to study the protective effect of PPs on peripheral blood, liver and spleen injuries in mice induced by IR. ICR (Institute of Cancer Research) male mice were administered orally with PPs (200 mg/kg b.wt.) once daily for 14 consecutive days prior to 7 Gy γ-radiations. PPs showed strong antioxidant activities. PPs significantly increased white blood cells, red blood cells and platelets counts. PPs also significantly reduced lipid peroxidation and increased the activities of superoxide dismutase, catalase and glutathione peroxidases, and the level of glutathione. PPs reduced the spleen morphologic injury. In addition, PPs inhibited mitochondria-dependent apoptosis pathways in splenocytes induced by IR. These results indicate that PPs are radioprotective promising reagents.

Evaluation of sesamol-induced histopathological, biochemical, haematological and genomic alteration after acute oral toxicity in female C57BL/6 mice

The objective of this study was to evaluate organ-wise toxicological effects of sesamol and determine the LD₅₀ cut-off value and GHS category following acute oral toxicity method OECD 423. An acute oral toxicity study was carried out in female C57BL/6 mice. Observations for physical behaviour and measurements on haematology, biochemistry, histology of vital organs were performed. In addition, genotoxicity assessment using comet and micronuclei assays was also performed. Acute toxicological effects were observed at 2000 mg/kg, while no adverse effects observed at 300 mg/kg. The effects of 2000 mg/kg were manifested as severe histopathological changes in all organs (femur, spleen, gastrointestine, lungs, heart, kidney, liver, stomach and brain) and excessive DNA strands breaks occurred in femoral bone marrow cells and splenocytes. A single dose of sesamol (2000 mg/kg, body weight) caused the death of two mice (out of three) within 2 h. Hence, sesamol is in GHS category 4 (>300–2000) with LD₅₀ cut-off value of 500 mg/kg body weight. In contrast, this study is correlated with the obtained GHS category 4 and LD₅₀ cut-off value 580 mg/kg body weight by ProTox. In conclusions, the present study has classified sesamol toxicity and assessed organ-wise acute oral toxicity of sesamol in female C57BL/6 mice. Therefore, these findings may be useful for the selection of dosages for further pre-clinical evaluation and potential drug developmental of sesamol.